package com.netease.nemo;

import java.security.MessageDigest;
import java.security.SecureRandom;

public class CheckSum {
    private static final String CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    // 计算并获取CheckSum
    public static String getCheckSum(String appSecret, String nonce, String curTime) {
        return encode("sha1", appSecret + nonce + curTime);
    }

    // 计算并获取md5值
    public static String getMD5(String requestBody) {
        return encode("md5", requestBody);
    }

    private static String encode(String algorithm, String value) {
        if (value == null) {
            return null;
        }
        try {
            MessageDigest messageDigest
                    = MessageDigest.getInstance(algorithm);
            messageDigest.update(value.getBytes());
            return getFormattedText(messageDigest.digest());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    private static String getFormattedText(byte[] bytes) {
        int len = bytes.length;
        StringBuilder buf = new StringBuilder(len * 2);
        for (int j = 0; j < len; j++) {
            buf.append(HEX_DIGITS[(bytes[j] >> 4) & 0x0f]);
            buf.append(HEX_DIGITS[bytes[j] & 0x0f]);
        }
        return buf.toString();
    }
    private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5',
            '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
    public static void main(String []args){
        String nonce=getRandom();
        System.out.println("nonce:"+nonce);
        String time = String.valueOf(System.nanoTime());
        System.out.println("curTime:"+time);
        System.out.println(getCheckSum("fc378b1eb486",nonce,time));
    }

    public static String getRandom() {
        SecureRandom random = new SecureRandom();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 22; i++) {
            int randomIndex = random.nextInt(CHARACTERS.length());
            char randomChar = CHARACTERS.charAt(randomIndex);
            sb.append(randomChar);
        }
        String randomString = sb.toString();
        return randomString;
    }
}
